The invention relates to a method of recording an information signal on a record carrier, an information signal being converted into a code signal comprising code words made up of bits, the number of successive bits of a first logic & value within the code word being at least equal to P, the number of successive bits of the second logic value within each code word, which are situated between the groups of at least Pbits of the first logic value, being at least equal to Q, P being an integer greater than or equal to 1 and Q being an integer greater than P, in which method an information pattern of recording marks corresponding to the code signal is formed on the record carrier, in which pattern the bits of the first logic value are represented by the recording marks.
The invention further relates to a record carrier with an information track in which information is recorded as an information pattern of recording marks, the information pattern comprising code symbols which represent code words, which code symbols have substantially equidistant symbol positions, a number of said positions being occupied by a recording mark, the number of consecutive occupied symbol positions being at least equal to P, the number of consecutive occupied symbol positions situated between the groups of at least P occupied symbol positions within the code symbols being at least equal to Q, P being an integer greater than or equal to 1 and Q being greater than P.
The invention also relates to a device for recording information on a record carrier, which device comprises an encoding circuit for converting the information signal into a code signal comprising code words, the number of consecutive bits of a first logic value in each code word being at least equal to P, and the number of consecutive bits of a second logic value within each code word, situated between the groups of at least P bits of the first logic value, being at least equal to Q, where P is an integer greater than or equal to 1 and Q is an integer greater than P, the device comprising drive means for moving the record carrier relative to the write means, which are adapted to form an elementary mark in response to a bit of the first logic value.
The invention moreover relates to a device for reading a record carrier on which an information signal is recorded as an information pattern of recording marks, which device comprises read means for scanning the information pattern and for generating a detection signal which is representative of the pattern being scanned, means for converting the detection signal into a code signal comprising code words, which code words are made up of bits of a first logic value and bits of a second logic value, and a decoding circuit converting the code signal into an information signal.
Such a method and such devices are known inter alia from British Patent Specification G.B. 2,148,670 (OSI 805). In the method and recording device described therein 8-bit information words, which constitute the information signal, are converted into 15-bit code words in which the number of successive "O" bits is at least two.
During reading the information pattern of recording marks is scanned by a laser beam, the reflected or transmitted laser beam being modulated by the information pattern being scanned. An optical detector detects the modulated laser beam, the detector generating a detection signal whose signal strength corresponds to the degree of modulation of the laser beam. Subsequently, the code signal is recovered from the detection signal by differential detection. In order to enable differential detection the code words should meet the additional requirement that during recording the number of "1" bits per code word is four for every code word. In that case every code word can be recovered reliably from the portion of the detected signal corresponding to the code word by differential detection. This is effected by selecting the four detection instants of most extreme signal strength.